| 长江河口地区全新世以来的弱透水层孔隙水地球化学特征及成因分析 |
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| 关键词:aquitard soluble salt porewater salt source water chemistry isotope |
| 基金项目:中国地质调查局地质大调查项目(编号: 1212011220005);国家自然科学基金项目(编号: 42007402; 41772327);江苏省自然资源厅自然资源发展专项(编号: JSZRHYKJ202106) |
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| Analysis of Geochemical Characteristics and Genesis of Aquitard in the Yangtze Estuary since the Holocene |
| The porewater of the aquitard reflects the original composition of the soil when it was deposited, and is of great importance for paleoclimate reconstruction. In order to analyze the recharge of aquitard porewater and its salt source since the Holocene in the Yangtze estuary, samples of labile salt, geotechnical, phreatic water, and nearshore seawater were collected. The hydrochemical characteristics of the porewater of the aquitard in the study area were determined using the soluble salt index combined with geotechnical parameters (water content, wet density, specific gravity). The recharge of porewater and its salt source were analyzed using the bipartite element method, Piper trilinear diagram, Gibbs diagram, and ion ratio method. The results showed that the mineralization of porewater ranged from 1.16 to 32.79 g/L, with an average value of 10.68 g/L. The percentage of haline water was the highest, followed by saline water and brackish water. The porewater type was dominated by Cl-Na type (85.6%), followed by Cl-Ca·Mg, HCO3-Ca-Na, HCO3-Ca, and Cl-Ca types in descending order. The local phreatic water type was HCO3-Ca and the deep porewater type was Cl-Na, indicating that the deep porewater sea retains the environmental information when the soil was deposited. The middle and shallow porewaters were affected by the surface effects such as atmospheric precipitation recharge, human activities and evaporation, and the porewater hydrochemical data were more discrete. The porewater δ18O and δD data indicated that the sample sites were influenced by both seawater mixing and evaporation, of which evaporation was stronger. The porewater seawater recharge ratio ranged from 30.2% to 87.0%, and the atmospheric precipitation recharge ratio ranged from 13.0% to 69.8%. The salt in the soil mainly originated from Holocene sea intrusion (sea source) with evaporative salt rock dissolution and feldspar weathering dissolution (crustal source). Taking deep porewater as an example, seawater recharge contributes 37% to porewater salinity, while the remainder was from crustal sources. |
| GOU Fu-gang,GONG Xu-long.2023.Analysis of Geochemical Characteristics and Genesis of Aquitard in the Yangtze Estuary since the Holocene[J].Acta Geoscientica Sinica,44(6):1063-1075. |
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